(1) Field of the Invention
This invention relates to any object that would require lineal (but not necessarily straight) forming whereby the forming process involves resistance being met by the forming tool during the forming operation on a workpiece such as sawing, routing, milling, drilling, shaping, or hammering, whether the forming motion of the forming tool is rotary, e.g. drilling, essentially linear, e.g. reciprocating saws, or linear-in-part, e.g. powered shears. This invention provides unique method of modulating the progression of the forming operation and a unique structure to lineally guide the formation operation either by guiding the forming tool into a workpiece or guiding the workpiece into the forming tool so that the workpiece can be safely and precisely formed without excessive damage to the workpiece with efficient use of the forming tool.
(2) Description of the Prior Art
Heretofore, material forming machines have either required the use of skilled and experienced operators to monitor and manually control the progression of the forming operation or used predetermined rates of progression of the forming operation that the operator judges best to approximate the optimum rate given the workpiece to be formed. Inasmuch as forming operations embrace a wide field of machining operations, the description of prior art will discuss rotary chip formation operations first.
Heretofore, cutters in which a rotary cutterhead require an operator to force the object across the table against an aligning device or fence using manual skill to vary the speed of the cut to prevent damage to the motor, drive train, cutting tips or edges, and the object to be cut.
A common example is a conventional wood table saw. The accuracy of the cut is no better than the trueness of the edge that is forced to ride against the aligning fence. Further, unless the operator is highly skilled at imparting a perfectly linear motion to the wood, the object may bind on the fence and correspondently bind at the saw blade causing the object to be imperfectly cut and worse, hurling the workpiece into the body of the operator. Although guards have been developed for the blade, the users of table saws often either wholly discard the guards or frequently do not operate them in place because the guards tend to bind the workpiece. Therefore the operators are endangered, because their hands pass by the exposed revolving blade and saw chips spray into their face from the blade that revolves toward the operator. Moreover, unless the operator is highly skilled, the wood object is not fed into the moving blade at a proper rate. If fed too fast, the motor is stalled and the saw may be damaged or the object is bitten into by the blade and thrown back into the operator. On the other hand, if fed too slowly, the chips taken out by the saw cutting tips gets so small that each tip does not bite, but rather skates or rides over the terminal surface of the cut allowing the saw blade to revolve at a high rate. Such cutting is not efficient, for saw blades are designed by rake, sharpness, and clearance angles and width of their teeth to efficiently operate in an optimum range of revolutions per minute in a given material. Moreover, such cutting may result in a damaged cut. The skating and resulting frictional heat produced along the sides and tops of the cutting tips results in a surface that is glazed, the wood cell structure bent over and crushed instead of cut, and the surface chemically altered by heating. This defect is also compounded by the workpiece binding at the fence or an operator pausing in feeding, usually causing a scorched band across the sawn surface. Such glazed surfaces are not acceptable for gluing, nor acceptable for application of a finish. Conventional table saws have had to be operated by expert operators. Moreover, conventional table saws require a high powered motor capable of delivering a relatively constant high RPM to overcome deviations from optimum rate of feed.
Another common example of prior art is a conventional table router in which the router bit protrudes upward and through a table's work surface with a fence or other aligning device on the top of the table. Again, the accuracy of the rout depends upon the trueness of the edge forced to ride the fence, and unless the operator is skilled in feeding against a fence, the workpiece binds and chatters resulting in distortion in the definition of the rout and chipped or torn woodgrain. Further, by too slow feeding, the wood surface may be scorched and skated upon and thus both chemically and physically deteriorated making the workpiece difficult to glue or finish properly. Similar to the table's saw blade, router bits are angularly and by the length of cutting edge designed to operate in an optimum range of revolutions per minute in a given material. By too slow feeding, the router bit revolves at an excessive rate resulting in inefficient cutting.
The same problems pertain to the use of conventional shaper, drilling, and milling machines. One of those problems being the necessity of expensive high powered motors delivering a constant high RPM to overcome deviations from optimum rate of feeding.
A workpiece of wood frequently contains hidden pockets of resin, hidden knots, and areas of interlocked and swirling grain and is generally of non-uniform density thus complicating the proper rate of feed, frustrating even a skilled craftsman. The edge forced to ride against a fence is often warped or out of true. Irregularly shaped workpieces requiring varying depths of cut of any material also complicate the proper rate of feed. Plastic and fiber build up material by variations of fiber structure present the same problem as wood to modulate the progression of cut.
The cutting, milling, and drilling of metal shares these problems. Instead of being scorched, metal becomes work hardened in the path of the cutter when the cutting edges are rotated at an excessive rate, for the skating or riding of the cutting edge produces excessive frictional heat.
Other forming operations that do not involve chip formation, nor involve rotary forming motion of the forming tool, such as powered shearing of sheet metal, heretofore, required the judgment of experienced operators to modulate the progression of the forming operation through workpieces of varying thickness. The same is true for other resistant forming operations where varying depths of the forming operation are sought with powered chisels or powered hammers. In these instances, if the rate of feed of the workpiece is excessive the forming tool motor slows as a result of the forming tool's motion being slowed by the resistance the tool meets in the forming operation and potentially damage results either to the machine or the workpiece. Heretofore, the machines utilized large and expensive forming tool motors and skilled operators to compensate and adjust for variances from optimum speed of feed.